Pyrolytic carbon has gained a lot of interest over the past few years as a bearing material in orthopedic applications. The material shows excellent wear characteristics, a modulus of elasticity similar to bone, and high strength. Pyrolytic carbon implants are commonly made by depositing a layer of pyrolytic carbon on a graphite substrate or core. Typically, pyrolytic carbon implants included a solid or non-porous bone fixation portion that is implanted into the bone and relies on a press-fit interference with surrounding bone tissue for fixation of the implant to the bone.
Bone on-growth or in-growth porous structures, such as porous tantalum and titanium structures, are sometimes used in orthopedic implants as the bone fixation component of the implant. Such porous structures are implanted into the bone and are designed to foster osseointegration. Osseointegration is the integration of living bone tissue within a man-made material. The porous structure and the bone material become intermingled as the bone grows into the pores. This intermingling of the bone tissue with the porous structure can enhance fixation between the orthopedic implant and the bone tissue. Because of the difficulties of bonding porous on-growth and in-growth structures to pyrolytic carbon and graphite surfaces, pyrolytic carbon implants have not included such porous fixation surfaces.